1. Field of the Invention
The present invention relates to a tire vulcanizer and in particular to a bead ring locking mechanism for restricting the turning of a bead ring with respect to a lifter.
2. Background Art
For example, a tire vulcanizer is disclosed in Japanese Unexamined Patent Application, First Publication No. H11-114965. This tire vulcanizer is equipped with a base for fixing a die via a platen, a central mechanism outer casing fixed to the base, a lifter arranged inside the central mechanism outer casing and moved upward or downward by a lower cylinder, and a bead ring attached to the upper end portion of the lifter to form a part of the die. In the tire vulcanizer, a tire is vulcanized inside the die.
A bayonet mechanism for allowing the bead ring to be engaged with the lifter is installed at the upper end portion of the lifter. The bayonet mechanism allows the bead ring to be engaged with the lifter in the axial direction, turning the bead ring in the circumferential direction when the lifter is moved upward, thus making it possible to release the engagement. Thereby, it is possible to remove the bead ring.
In a tire vulcanizer having the above-described bayonet mechanism, in order to prevent the engagement of the bead ring with the lifter in the axial direction from releasing by turning the bead ring in the circumferential direction from a state of being engaged with the lifter in the axial direction, a set screw is used to stop the turning of the bead ring. Specifically, as shown in FIG. 7, an annular lower bead ring 51 is attached to the outer circumferential face of a tubular lifter 50. Then, the lower bead ring 51 is fixed to the lifter 50 by screwing the set screw 53 into an attachment hole 52 of the lower bead ring 51.
However, the lower bead ring 51 which forms a part of the die must be frequently exchanged in accordance with each time tires to be manufactured are changed for the type and the size. In order to replace the lower bead ring 51, it is necessary to frequently fasten or loosen the set screw 53. After repeating this operation, the fastening of the set screw 53 into the attachment hole 52 gradually loosens, and the lower bead ring 51 is turned with respect to the lifter 50 during the replacement of the lower bead ring 51. Therefore, the lower bead ring 51 must be checked frequently, sometimes the ring 51 must be replaced.
Further, since the leading end of the set screw 53 fastened on the lower bead ring 51 is in point contact with the outer circumference face of the lifter 50, a similar failure as that described above may take place, if the set screw 53 is not sufficiently fastened.
An object of the present invention is to provide a bead ring locking mechanism of a tire vulcanizer capable of reliably stopping the turning of a lower bead ring with respect to a lifter and also replacing the lower bead ring easily.